PLASMA-CONCENTRATION OF ESTRADIOL AFTER TRANSDERMAL ADMINISTRATION OFSYSTEN(R)50 (EVOREL(R)) OR MENOREST(R)50

Circulating plasma levels of 17 beta-estradiol after the administratio n of fixed dosages of 17 beta-estradiol show great variability dependi ng upon product formulation, route of administration, and interindivid ual variation in absorption and metabolism. Two new 17 beta-estradiol transdermal delivery systems, Systen(R)50 (also called Evorel(R)) and Menorest(R)50 have recently been approved in Europe for the treatment of climacteric symptoms. Both transdermal systems deliver 17 beta-estr adiol at a rate of 50 mu g/day. The present study was undertaken to co mpare the plasma profiles of 17 beta-estradiol delivered by these 2 pr oducts in 30 healthy postmenopausal women according to a randomised,mo nocentric, single-blind, crossover protocol. Two 4-day patch applicati on periods were separated by a 7-day washout period. Plasma 17 beta-es tradiol concentrations were determined 24 hours and 30 minutes before and then 0, 2, 4, 8, 12, 24, 48, 60, 72, 84 and 96 hours after the fir st patch administration. 17 beta-Estradiol measurements were performed using a specific direct radioimmunoassay developed at the French Fond ation de Recherche en Hormonologie laboratory. Bioequivalence was asse ssed by analysis of variance. The results demonstrated that the 2 prod ucts were similar in terms of maximum plasma concentration; however, m ean concentration, concentration at 96 hours and area under the concen tration-time curve were significantly (p < 0.05) greater with Menorest (R)50. Furthermore, 17 beta-estradiol concentrations decreased more ra pidly with Systen(R)50 than with Menorest(R)50. These differences in t he plasma profiles of 2 transdermal systems both delivering 50 mu g/da y of 17 beta-estradiol may have important clinical consequences both i n terms of tolerance and effectiveness.